I just tried upgrading from LibreOffice-4.1.x to 4.2.2, on Slackware 14.1. I am using the binaries from libreoffice.org as I have always done with prior releases, unpacking the RPM files and installing them myself. Never had this problem before.

When I try to start LibreOffice-4.2.2, it sometimes fails after displaying the splash screen with this message:
I'm not using "su" to switch users, and I know how Xauthority, DISPLAY, etc. all works. That isn't what is wrong here. The crazy thing is how this is failing most of the time, but not always. Just now I tried to start it with the exact same command 20 times, one right after another. (If it worked, I immediately quit from Libreoffice). It worked 7 times, and failed 13 times.

I've tried strace on it, and it didn't help. I can see it connect to the X socket, open and read .Xauthority, send credentials to the X server, and get the error message back. There is nothing in the xdm or Xorg log files.

I tried to watch it with wireshark, but when it uses TCP to talk to X it doesn't fail. It only fails when using UDS, and Wireshark can't see UDS. (That it never fails with TCP is probably a clue.)

Any ideas on what is wrong? My top suspect is a library conflict, but I don't know what libraries can cause this type of intermittent but frequent failure.

Update: This is apparently not Slackware-related. Firefox went through this same problem a few years ago, caused by a race condition with connections to the X server, between a parent and child process. It only happens when using the XDM login manager.

There is a work-around if anyone else is having this problem: disable one of the 2 types of X11 authentication methods by placing the following in /etc/X11/xdm/xdm-config:
This disables the other type, XDM-AUTHORIZATION-1, which has the problem with the race condition. I can confirm this worked.

I will follow up with LibreOffice.

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